Various sputter techniques have been used to deposit thin films over substrates. Deposited metal films on thin film semiconductor devices can be formed by a magnetron sputtering apparatus or other known sputtering techniques. As is well-known to those in the field, the magnetron sputtering apparatus delivers plasma ions of a gas to a target at a velocity sufficient to cause target surface particles to leave the surface and be predictably deposited as a thin layer or film on the surface of a substrate. The sputtering source can be a planar target, and ejected atoms travel predictably along a line-of-sight trajectory to deposit, for example, as a top layer on a semiconductor wafer whose deposition surface is oriented parallel to the erosion face of the target.
Hollow cathode magnetron (HCM) sputtering targets are produced in the shape of an inverted crucible or bell and are used as target materials. An inner chamber or cavity defined by the HCM target contains a plasma that erodes the interior wall surfaces of the target during use. HCM sputtering targets are useful and desired for their ability to deposit a film able to fill deep and narrow channels in a substrate. This is accomplished as target atoms, ejected from the interior walls of the target become ionized as they pass through the plasma. Magnetic fields then traject the ions in a direction perpendicular to the substrate. One disadvantage of the known HCM sputtering techniques is that the desirable film deposition uniformity they provide to a surface is brought about at the expense of significant non-uniform target erosion. Uneven target erosion eventually leads to uneven or non-uniform layer deposition on a substrate material. This, in turn leads to a potentially low number of acceptable products, such as wafers, being produced from each HCM target. Therefore, in designing a useful HCM sputtering target, two critical goals are a uniform erosion of the target and a uniform deposition of target material on a substrate.
Many attempts to improve target erosion uniformity have been made and are discussed and otherwise referred to in U.S. Pat. No. 6,887,356. However, many known HCM systems are either too mechanically complex, or do not adequately solve the problems of non-uniform target erosion leading to non-uniform film deposition on a substrate.
In semiconductor manufacturing Rs non-uniformity of sputtered films (deposited film thickness) is an important quality measure. Current technology approaches attempt to minimize Rs non-uniformity by controlling the texture and grain size of sputter targets. Therefore it is desirable to further improve deposited film Rs non-uniformity through the development of improved targets by optimizing the texture and grain size of 300 mm Cu HCM sputter targets.
U.S. Pat. No. 7,041,204 discloses that grain size is known to influence deposited film uniformity and is preferably less than about 100 microns. This patent further discloses a desire to increase magnetic flux pass through of a target by achieving a high degree of grain orientation (texture) in the (200) orientation via a common cold working process in a unidirectional method to achieve the desired texture and retains the resulting cold working stresses to achieve the desired increase in magnetic flux pass through.
U.S. Pat. No. 6,887,356 discloses a tantalum HCM target with substantially uniform grain size and texture. Grain size ranges from 5 ASTM+−2 (125 to 32 microns). This patent discloses employing a cold rolling process similar to the '204 patent, and maintains cold working induced stresses in the final target. In addition, the '356 patent cites dispersed textures of (111)-(100).
However, none of the known methods presented above have solved the critical issues leading to the non-uniform erosion of HCM targets. An improved method of manufacturing acceptable HCM targets would be highly advantageous to the industry.